I have done that too - be careful with the paper sizes in Lightroom! This is equally true of all roll-fed printers. I use mostly custom sizes ( the exception is that ARCH D is a perfect 24x36", so no need to make another) with the width ALWAYS being 24" (unless you have a 17" roll in your 24" printer, or are printing on a sheet). I have a bunch of custom sizes set up with different lengths depending on what I'm doing. All of my custom sizes are set up with all four borders at 0.25"
24x18" is a really useful one (note that the ARCH C 24x18" size is oriented the WRONG WAY - it will print only 18" wide and use up a 24" long piece of paper)... It makes a nearly 16x24" print (from a 3:2 image), or two nearly 12x18" prints next to each other.
24x20" is very useful if you use a less elongated format like Micro 4/3 or most medium format. I have had it set up in the past - haven't needed it yet with this printer.
24x14" is useful, because it gives handling room on the top and bottom when making three 8x12s next to each other.
24x36" (ARCH D) is useful to get the largest possible print of the entire frame.
24x8" is useful for cramming a bunch of 5x7" prints next to each other, and 24x9" is useful for 6x9" prints.
I keep a couple of longer sizes handy for dealing with panoramas - 24x72" is my record so far, and it's about the longest I can print at high resolution from Lightroom on my MacBook Pro with 16 GB of RAM.
Note that most of my print sizes are a tiny bit short of nominal (my 16x24" print is actually 23.5" wide, for example). I take this into account when ordering mats, but it's cheaper than running prints the long way to get the last bit (and you can't get a true 24x36" without going borderless).
Dan
